Evaluation of Two Circumaural Earphones for Audiometry.

Objective: The Sennheiser HDA 200 earphone, a standard circumaural earphone used in audiometry for many years, is out of production and is replaced by the RadioEar DD450. The Sennheiser HD 280 Pro earphone is a consumer product that has characteristics that may be suitable for audiometry and may be a low-cost alternative to the DD450. The DD450 and HD 280 Pro earphones were compared with the HDA 200 for use in audiometry.

Delay of poliovirus plaque formation with use of fresh bovine serum in the growth medium of host cells.

The plaque formation of poliovirus in HeLa cell monolayers was decreased upto 95% when the host cells were subcultured several times in a growth medium containing fresh bovine serum prior to their inoculation with virus. Extended incubation of infected cell monolayers indicated that the inhibition was in the form of a delay in plaque formation rather than a permanent inhibition of it. The inhibitory factor, which was found in most bovine sera, was very unstable and disappeared after storage of the serum at -20 C for a few weeks or at 36 C within a few days.

INFECTIVITY OF POLIOVIRUS AND ITS NUCLEIC ACID FOR DEHYDRATED HELA CELL MONOLAYERS.

Smull, Christine E. (The Geisinger Medical Center, Danville, Pa.), and E.